Fast assembly of bio-inspired nanocomposite films
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Marianne Dietiker Laboratory for Nanometallurgy, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
Michael Plötzea) and Lee Yezek Laboratory for Clay Mineralogy, Institute for Geotechnical Engineering, ETH Zurich, 8093 Zurich, Switzerland
Ralph Spolenak Laboratory for Nanometallurgy, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland
Alexander M. Puzrin Laboratory for Clay Mineralogy, Institute for Geotechnical Engineering, ETH Zurich, 8093 Zurich, Switzerland (Received 30 October 2007; accepted 17 January 2008)
This paper presents a spin-coating layer-by-layer assembly process to prepare multilayered polyelectrolyte-clay nanocomposites. This method allows for the fast production of films with controlled layered structure. The preparation of a 100-bilayer film with a thickness of about 330 nm needs less than 1 h, which is 20 times faster than conventional dip-coating processes maintaining the same hardness and modulus values. For validation of this technique, nanocomposite films with thicknesses up to 0.5 m have been created with the common dip self-assembly and with the spin coating layer-by-layer assembly technique from a poly(diallyldimethylammonium)chloride (PDDA) solution and a suspension of a smectite clay mineral (Laponite). Geometrical characteristics (thickness, roughness, and texture) as well as mechanical characteristics (hardness and modulus) of the clay-polyelectrolyte films have been studied. The spin-coated nanocomposite films exhibit clearly improved mechanical properties (hardness 0.4 GPa, elastic modulus 7 GPa) compared to the “pure” polymer film, namely a sixfold increase in hardness and a 17-fold increase in Young’s modulus. I. INTRODUCTION
Multilayered polymer-clay nanocomposites have attracted considerable attention due to their mechanical properties, which resemble those of naturally occurring composite materials with layered brick-and-mortar structure, such as nacre.1,2 The composite materials are constituted of hard components (e.g., silica particles, fibers, carbonates, and clay platelets) and soft material (e.g., positively charged polymers); each brings into the system its particular qualities. While the hard phase (the “brick”) provides stiffness and mechanical stability to the system, the function of the matrix (the “mortar”) is to maintain the geometry of the structure and to distribute the mechanical stresses among the hard constituents, providing at the same time high fracture toughness and ima)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2008.0147 1026 J. Mater. Res., Vol. 23, No. 4, Apr 2008 http://journals.cambridge.org Downloaded: 18 Mar 2015
proving the fatigue resistance. Several toughening mechanisms like crack blunting, branching and deflection, platelet pullout, crack bridging, and sliding of platelet sublayers allow higher energy consumption.3–5 Different layer-by-layer (LBL) assembly techniques, based on sequential adsorption of oppositely charged compounds, have been established for p
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